1. Field of the Invention
The present invention relates to piano action mechanisms having jacks, particularly, for use in grand pianos.
2. Discussion of the Background Art
The piano is a keyboard instrument which allows a performer to play both delicately and softly as well as forcefully and loudly. The action is a responsive mechanism whereby a performer can control tone, volume, sustainable tones, and tone quality. Piano strings are struck by hammers and the action provides an escapement mechanism which allows the hammer to leave a "jack" as it approaches the string. After the hammer is thrown against the string by striking a key which actuates the jack, it is free to bounce back after striking the string. This is necessary for the production of a clear unmuffled tone. Escapement and repetition movements are also important functions of the action and should be reliable and precise.
The conventional action mechanism of a grand piano typically includes a linkage having a whippen with a rear end pivotably attached to a flange on a whippen rail and which is propelled upwardly by a capstan screw fastened to a central portion of a key when the key is depressed. The motion of the whippen is transmitted to an L-shaped jack pivoted to the front end of the whippen and an upper end of the jack passes through an elongated hole of a repetition lever to propel a knuckle attached to a hammer shank upwards such that a hammer is driven toward a string to strike it.
In the conventional action mechanism, the force of a finger depressing a key is transmitted from the key to the whippen, from the whippen to the jack, from the jack to the knuckle of the hammer shank, and the force is finally transformed into an arcuate rotational motion of the hammer for producing a particular sound. With such a mechanism or linkage, a particular touch feeling is obtained in playing the piano.
Escapement disconnects the hammer from control of the key a short distance before the hammer strikes the string and is necessary to allow the hammer to rebound from the string and not be blocked against it. A typical grand piano whippen employs the jack to transmit motion from the key to the hammer. This type of jack is nothing more than a prop-stick under compression, which is yanked out of the system an instant before the hammer strikes the string. Articulated jacks are hinged in the middle and unlike the prop-stick jack which is yanked out of the system at the appropriate moment, the articulated jack simply hinges and collapses, permitting escapement with relatively little friction.
It is highly desirable to have an action that has low friction and high stability during operation and is precise in its operation with little play in its linkage. It is also highly desirable to have an action with better dynamic control and one that causes less player fatigue and that is easier and less expensive to construct and regulate than actions presently available. The action should be more wear-free and stable over the long haul. Note-to-note dynamic response should be more uniform. It is also desirable for the newly designed action to have a whippen with the above mentioned attributes and interchangeability with a standard whippen. Prior art actions have a high amount of friction at the jack and knuckle interface and it is desirable to eliminate this.